How many mountain bikes are sold today with the ability to trim their front derailleur? In light of that, are there any truly micro-index shifters available where you can dial in enough movement to shift from one ring to the other and then dial up/back as needed to keep it from rubbing? I sort of saw a prototype at Walmart when one of their display models was incorrectly installed with the right 8-speed shifter mounted to adjust the chainrings